Arrangements of instruments (moving iron or moving coil) consisting of an axis and the moving iron or moving coil inclusive of the associated arms attached to the axis, are known from the DE-PS No. 18 16 963. Although the embodiment provided there for the axis has proved itself, the installation of the moving member with its arm at the axis required there is very cumbersome and thus time-consuming and expensive. This is so because this installation has to occur by insertion of the axis into the bores at the ends of the arms. Such a threading-in must be made by hand or it has to be done automatically with very great expense. Both are no longer acceptable because they are considered approaches which have no proper rationale.
Additionally, there is the danger that, in the course of the threading-in operation, the very delicate pivot points impact at the ends of the arms or next to the respective bore and thus could be damaged. Additionally, 3 there is another disadvantage, in that the riveting provided in this previous publication is possible at only one of the arms of the moving member with the collar at the axis, since in view of the previously mentioned requirement of the threading-in operation, one cannot provide two collars at the axis for riveting of both arms of the moving member. If the moving element, however, is riveted solidly only with one arm and if it is retained with the other arm only loosely or with a more or less solid seat at the axis, then this can lead to an unstable attachment of the moving element particularly in the case of larger and thus heavier moving members. This entails an impairment of the reproducibility of the so-called scale characteristic, meaning the respective indication of the moving member. This disadvantage is considerable since these scales must be reproducible because of cost consideration and since it is impossible to fabricate a special scale (after the appropriate graduation) by hand for each moving member. If the moving member is designed as a moving coil, then it has to be added so that, particularly in the case of larger and thus heavier moving coils, such a moving member attached so-to-speak "on one hip", no longer has a sufficient stability because of the coil weight. Only one arm can be riveted on. If another arm exists which cannot be riveted on, then this arm can only be inserted or slid on upon the axis. Then, because of the fabrication tolerances there is the danger of vibration of the moving member with respect to the axis.
In the case of a too solid counter-clamping of the second arm upon the axis there is the danger of distortion. It has also to be taken into account that other components are attached on the axis, such as the indicating cross and the dampening vane and that these parts must have a specific relationship (angular position) in circumferential direction with respect to the moving member. Thus, the moving member must also be adjusted in the circumferential direction during its attachment at the axis. This can result in difficulties during the fabrication in the explained state of the art.
It is indeed known from the DE-PS No. 19 19 244 to insert a small moving iron plate into slits of collars, which are in one piece with the axis according to the DE-PS No. 18 16 963. This permits, however, only an attachment of flat small moving plates extending in radial direction, not, however, the attachment of moving irons in the shape of circular segments and of moving coils, which are both respectively provided with arms for their attachment at the axis. Moving irons in the shape of circular segments are, however, required for many applications. An arrangement according to the above-mentioned patent publication DE-PS No. 19 19 244 thus does not address the thrust of the present invention. Furthermore, this prior arrangement has an additional disadvantage in that, for the adjustment of the moving member in longitudinal direction of the axis in addition to the attachment collars, at least one adjustment stop must be provided at said axis. The attachment of small moving iron plates at the collars occurs only along very small cross-sections and therefore can again detach itself.
Contrary to that, a primary task of the invention is to provide a simpler as well as stable attachment of moving members at the axis which can be accomplished with correspondingly smaller costs, whereby the moving members are designed as moving coils or as circular segment-shaped moving irons respectively with associated arms.